By way of background, in marking systems such as Xerography or other electrostatographic processes, a uniform electrostatic charge is placed upon a photoreceptor belt or drum surface. The charged surface is then exposed to a light image of an original to selectively dissipate the charge to form a latent electrostatic image of the original. The latent image is developed by depositing finely divided and charged particles of toner upon the belt or drum photoreceptor surface. The toner may be in dry powder form or suspended in a liquid carrier. The charged toner, being electrostatically attached to the latent electrostatic image areas, creates a visible replica of the original. The developed image is then usually transferred from the photoreceptor surface to a final support material, such as paper, and the toner image is fixed thereto to form a permanent record corresponding to the original.
In these electrostatic marking systems, a photoreceptor belt or drum surface is generally arranged to move in an endless path through the various processing stations of the xerographic process sequentially, such as a charging station, an exposure station, a development station, a transfer station, a detack station, a fusing station, and a cleaning station (see FIG. 6 of this disclosure). Sometimes, as noted, the photoreceptor or photoreceptor surface is in the form of an endless belt and in other systems it is in the form of a drum. In this endless path, several xerographic-related stations are traversed by the photoconductive belt or drum, and become worn. Each of these belts is exposed to friction and moved by rollers that provide the belt movement to accomplish the belt purpose. Since the photoreceptor surface is reusable when the toner image is transferred to a final support material such as paper, the surface of the photoreceptor (PR) is constantly abraded and cleaned by a blade and/or brushes and prepared to be used once again in the marking process. The transfer process from the PR to paper uses mechanical devices, such as transfer assist blades which can also have adverse effects on the PR.
Transfer Assist Blades are devices which apply pressure to the back side of a sheet of media in the transfer zone of a xerographic printing machine. The pressure holds the media against the photoreceptor to improve the transfer of toner to the media. Transfer Assist Blades are mechanical devices that wear and require frequent replacement. These mechanical devices are moved in and out of a functional position as each sheet of paper enters and exits the transfer zone. If the device is in the functional position between sheets of media, the blade will become contaminated with toner from the inner document patches used for xerographic setups. This contamination can then be transferred to the back side of future media sheets, and this is an undesirable condition.
The function of the Transfer Assist Blade in the prior art is to apply a pressure to the back side of a media forcing it against the photoreceptor. This pressure is applied currently by forcing segments of the Transfer Assist Blade against the media by lifting specific segments with lifter fingers. The Transfer Assist Blade is comprised of many independent segments. The lifter fingers are also comprised of several independent fingers. These independent segments and fingers are activated based upon the width of the media currently being printed. If the media is narrower than the full process width, the inboard segments and lifter fingers are not engaged, as media enters the Transfer Zone. If they were activated, the blade segments would contact the photoreceptor causing scratches on the photoreceptor surface. These scratches would first cause potential defects in the customer prints once a full width media was being printed again. Second, the life of the photoreceptor would be reduced because of these scratches, driving up printing costs.